Just bought a 2017 Keystone 21FQ that has the entire back end of the trailer as a huge u-shaped dinette with an enormous rear window (that I already know I am going to have to carry a ladder to wash window from outside) and two good-sized side windows.
Originally I thought I wanted a small slide with a u-shaped dinette in it, until I thought about the last 4-5 times we'd taken the old trailer (an unloved 2011 FR Wolf Pup) out - each time, the view or the private area of the campsite was right behind the trailer and a slide on the utility side would just have me staring at someone else's RV.
Also the slide added another 500-800 lbs that we didn't need to tow. It IS nice that the slide opens up the center of the trailer, but I traded views for space. Trailer box on this is 21', it is 25'6" from the spare tire on the back bumper to the tip of the hitch receiver.
Now watch, everywhere we stay in this trailer will be looking at a wall out the back....
TT: 2017 Keystone Hideout 21FQWB (prior 2011 FR Wolf Pup, 1990 Starcraft tent trailer, tent camping)
TV: 2013 Ford F150 5.0 V8, 373
(map is where I've camped, not where I've lived or visited)